In a conventional static random-access memory (SRAM), a bitcell connects to a pair of bit lines during a read operation. Prior to the read operation, the bit lines are pre-charged to the power supply voltage used for the bitcell. Depending upon the binary content of the bitcell, the bitcell will slightly discharge either the true bit line or the complement bit line in the bit line pair from its pre-charged state. For example, suppose that the bitcell is storing a binary one. During a read operation, a word line is asserted so that the bitcell is coupled to its bit line pair. Due to the binary one value, the complement bit line will then be discharged from its pre-charged state. But the bitcell will maintain the true bit line at its pre-charged state. The read operation will thus develop a voltage difference across the bit line pair. This bit line voltage difference is not full rail but instead equals a fraction of the power supply voltage. For example, if the power supply voltage is one volt, the voltage difference may be just 100 millivolts or less. To respond to this relatively small voltage difference and make a bit decision as to what was stored in the bitcell, a typical sense amplifier requires a relatively large amount of gain.
Accordingly, there is a need in the art for memories having increased density and improved power efficiency.